EP0814280B1 - Double mass damper containing easily mountable torque limiter - Google Patents

Abstract

The shock absorber comprises a first mass (12) rotating with an input shaft (24). A second mass (24) rotates coaxially on the first mass by means of ball bearings (20). These constitute a friction clutch reaction plate (86) which rotates on the output shaft. The two masses are coupled together by an interposed flexible washer. The second mass has a first part (64) able to rotate freely on the first mass and a second part (66) which rotates on this first part. These constitute a friction clutch reaction plate (84). Friction torque limiters (98) are arranged between the first and second parts of the second mass. The external ball bearing track (21) is constituted by the peripheral internal edge of the first part of the second mass.

Description

The invention relates to a double damper flywheel, for the rotational coupling of a motor to a transmission, in particular intended for a motor vehicle, comprising two steering wheel elements, primary and secondary, mounted coaxial and integral in rotation respectively with the motor shaft and an input system member transmission, coupling means connecting the two elements of steering wheel allowing an angular offset between them to against an elastic return torque, and means friction dampers in parallel on the coupling means, the secondary flywheel element comprising a torque limiter between a hub on which the coupling means are articulated and an annular inertia disc constituting the reaction plate a friction clutch forming an input member of the transmission, the disc having a central bore surrounded by a veil part limited by internal and external faces perpendicular to the axis of rotation of the steering wheel, while the hub has an annular groove open on the outer side in direction opposite to the primary steering wheel, bounded by a background cylindrical suitable for centering the central bore of the disc, and internal side by a clean side to carry on the internal face of the veil, this being maintained with friction adjusted in the groove by a friction washer secured in rotation to the hub and pressed against the outer face of the web by a washer axial elasticity secured to the hub.

We know that double damping flywheels, in particular as described in SAE publication 950893: RADIAL DUAL MASS FLYWHEEL, have been designed to dampen the vibrations of torsion created by piston engines and applied to transmission system of a motor vehicle. They constitute high-cut resonant mechanical filters with cutoff frequency mainly determined by stiffness coupling means and the inertia of the steering wheel element secondary and organs which are secured to it in rotation, while amortization is provided by the means friction dampers, dissipative. Double steering wheels shock absorbers are designed so that their cutoff frequency is lower than the fundamental frequency of vibration corresponding to the engine idling speed. That is particularly good in double flywheels so-called radial dampers, as described in the publication cited above, comprising extended coupling means radially in the absence of transmitted torque, including the stiffness apparent in rotational drive, zero in the absence of transmitted couple, grows with this couple. In addition, the radial arrangement of the coupling means authorizes a large angular travel with high transmitted torque (which can reach almost 90 ° on either side of the neutral position) favorable to low torque damping accuracy transmitted, where the angular movement is still noticeable.

However, these qualities in normal operation have a counterpart to the launch of the engine, this passing necessarily then by the speed which corresponds to the resonance of the filter, while the moment of inertia of the element secondary steering wheel from the immobility caused on the coupling elements brutal traction, which risks deteriorate.

To avoid these drawbacks, and therefore a premature deterioration of the double shock-absorbing flywheels, it has been necessary to equip these flywheels with torque limiters as for example described in document FR-A-2 618 201. Such limiters can be arranged between the articulation of the coupling means and most of the mass of inertia of the secondary flywheel element, these torque limiters are adjusted to slip in response to an excessive attack torque, with the creation of an offset irreversible angular which clips the torques applied to the transmission system (the excess energy supplied by the torque being dissipated by slip friction), and prevents damage to the steering wheel components. Of course, the limit torque, beyond which slippage occurs, must be greater than the maximum useful torque of the engine, without however exceeding this maximum torque much, to be effective.
Friction torque limiters, operating generally between a driving member and a driven member capable of coaxial rotations, typically comprise circular friction tracks, centered on the axis of rotation of the members, and in mutual support under the action of spring means with axial elasticity. The limit torque (without slippage) is determined by the reciprocal bearing force of the tracks provided by the spring means, the coefficient of friction between tracks, and the radius thereof.

In the case of double shock-absorbing flywheels, it is known from the state of the art, in accordance with the preamble to the claim 1, that the driving member is a hub on which articulate the coupling means, and that the driven member is a annular inertia disc with a central bore which engages on a cylindrical seat formed in the hub. Around of the bore, the disc is in the form of a veil with faces perpendicular to the axis of rotation of the steering wheel. The hub has an annular groove open on the outer side in direction opposite to the primary steering wheel, with a bottom formed by the peripheral cylindrical centering span, and a flank machined on one side to wear on a first side of the veil, while an axially elastic washer secured to the hub constitutes second flank of the groove and requests the second face of the veil to clamp the first face of the veil against the first flank of the hub groove.

But the washer with axial elasticity cannot bring to flat on the second side of the veil, the directed elastic reaction axially resulting from a deformation with a gradient according to the radius. Imperfect reach, acting on a surface reduced, joined to the great hardness that must have the washer in order not to undergo plastic deformations, would lead to a erosion of the second face of the web in contact with the washer. A friction washer, or of application, between the second face of the veil and the washer axial elasticity must be secured in rotation with the hub to prevent slipping between this friction washer and the elastic washer axial, while having a certain freedom of movement axial with respect to the hub, to transmit effectively to the veil the thrust of the axial spring washer, by wearing flat on the second side of the veil.

The mounting of a double damper flywheel, which includes the assembly of a large number of organs, some of which under elastic prestressing, mostly housed between primary and secondary steering wheel components, and subjugation of these organs together in operating position, assumes a meticulous choice of the locations of these organs, and in particular of those of these organs which must be functionally arranged between the two steering wheel elements, as well as the assembly order.

The mounting of the torque limiter, which does not require of connection with the element of primary steering wheel, will thus be carried out advantageously from the outside of the steering wheel, and therefore from the side accessible (external side) from the secondary steering wheel element, at center of the external face of the disc, the face which forms a clutch reaction, input system member transmission.

It will be observed that, practically, it is necessary that the throat is practiced in the hub, because if we practiced the groove in the disc, while the hub would have a web, engagement of the disc on the hub (mounting the disc does not can precede that of the hub) would suppose that the groove is open from the inside, which would require placing the friction washer and the axial spring washer on the inner side of the disc, which would seriously complicate their mounting.

We saw above that the friction washer should be secured in rotation with the hub, while remaining free in axial movement. Conventionally, such joining would be obtained by practicing grooves, parallel to the axis of rotation in the outer periphery of the simbleau, and by providing the inner periphery of the friction washer of teeth complementary to the grooves. However, the machining of the grooves requires the execution of a series milling at regular angular spacing, and turns out expensive. To avoid machining the grooves, we can consider use a solution in which the washer friction and the axial spring washer form a single and even room.

To reduce the machining cost, the invention provides a double damper flywheel, for the rotational coupling of a engine with a transmission system, in particular intended for a motor vehicle, comprising two steering wheel elements, primary and secondary, mounted coaxial and integral in rotation of the motor shaft and of a member respectively transmission system input, coupling means connecting the two steering wheel elements allowing an offset angular between them against a recall couple elastic, and friction damping means in parallel on the coupling means, the secondary steering wheel element having a torque limiter between a hub on which articulate the coupling means and an annular disc of inertia constituting the reaction plate of a clutch to friction forming the input member of the transmission system, the disc having a central bore surrounded by a part in sail limited by perpendicular internal and external faces to the axis of rotation of the steering wheel, while the hub has a annular groove open on the external side in a direction opposite to the primary flywheel, delimited by a cylindrical bottom suitable for center the central bore of the disc, and on the internal side by a clean side to wear on the internal face of the veil, this one being maintained at friction adjusted in the groove by a washer friction secured in rotation to the hub and pressed against the external face of the veil by a washer with axial elasticity secured to the hub, characterized in that the friction washer has legs straightened outwards and crossing holes in the axial resilient washer.

Thanks to this arrangement, the centering range of the hub is cylindrical and smooth, and the friction washer is secured in rotation to the hub by means of the axial elastic washer, itself secured to the hub, while that axially it is free to come to bear on the external face of the veil, the passage of the legs in the holes of the washer with axial elasticity allowing the desired axial play. Expression "stowed" means that the axial spring washer is restricted in movement relative to the rotating hub and axially. Friction and axial spring washers are made by cutting and stamping with a front press heat treatments, at minimal cost. The washer friction completes the throat by forming the other side of it.

Preferably, the washer with axial elasticity is riveted on the hub, which constitutes a lashing particularly simple.

Also preferably, the washer rivets to axial elasticity form pivots for medium bearings hitch. These pivots must be fixed on the hub, so that riveting performs a double subjugation in a single surgery.

To carry out this riveting, the element of primary flywheel, opposite the location of the rivets axial spring washer when the return torque of the coupling means is zero, orifices for the passage of a riveting rivet.

In preferred arrangement, the elastic washer axial transversely includes an internal peripheral part with holes for securing the washer, and below a fold in step, an elastically frustoconical central part deformable. This central part forms a Belleville washer, and its deflection does not extend to the peripheral part internal, the fold in steps preventing the transmission of deformations.

So we prefer that the legs straightened towards the outside of the friction washer protrude from the inner periphery of this washer, and that the orifices of passage of these legs are made in the fold step. The coaxiality of the primary and secondary steering wheel elements is ensured by a ball bearing with an inner ring mounted on a protruding sleeve of the steering wheel element primary. Preferably, the hub of the steering wheel element secondary is made of hardened metal and constitutes the outer ring of the rolling. The thickness of the outer ring of the bearing, in a place where the bulk is significant, and we saves costly range hardening operations centering and flank of the groove. In addition, overall machining operations of the different parts, we save the machining of the periphery of the outer ring, and above all that of the housing of a bearing ring in the center of the hub, with the necessary fine adjustment play. Finally the hardening of the metal which constitutes the hub improves the conditions of friction between disc and hub.

It will be appreciated that the veil of the inertia disc has a thickness reduced compared to that of its part main.

• la figure 1 est une coupe, passant par l'axe, d'un volant double amortisseur conforme à l'invention ;
• la figure 2 est une vue partielle du volant de la figure 1, montrant le limiteur de couple.

Secondary characteristics and advantages of the invention will emerge from the description which follows by way of example, with reference to the appended drawings, in which:

• Figure 1 is a section through the axis of a double damper flywheel according to the invention;
• Figure 2 is a partial view of the steering wheel of Figure 1, showing the torque limiter.

As a whole, the double shock-absorbing steering wheel shown in the figures usually comprises a primary flywheel element 1, fixed on an end flange 8a of a motor vehicle engine crankshaft by bolts 8b, and centered on a general axis of rotation of the flywheel XX 'by a bore engaged on a cylindrical end piece 8 of the flange 8a, and a secondary flywheel element 2 as a whole mounted coaxial with the primary element 1 via a ball bearing 25. Coupling means 3, consisting of cassettes or coil springs are caught between windows of a mid-veil drawer and pairs of half-housings formed in a housing, articulated by a bearing of housing on a pivot 5 held, near the periphery outside, in the primary steering wheel element, and by a bearing drawer, close to the XX 'axis on a pivot 20a riveted on the secondary flywheel element 2. In the absence of a torque transmitted from one steering wheel element to another, the pivots, directed parallel to the axis XX ', are aligned radially :. when torque is transmitted, the coupling means 3 are put in traction, with compression of the coil springs, elongate and arrange themselves obliquely, the elastic reaction force of springs then having a tangential component.

Also commonly, damping means with friction 4 with axial action, comprising a stack of friction washers secured alternately to the elements primary and secondary and pressurized by a washer Belleville, are arranged functionally in parallel on the coupling means 3, here fixed on one side to the steering wheel element primary 1 and driven on the other by the pivot 20a engaged in a fork.

According to the invention, the steering wheel element secondary 2 consists of a hub 20, and an inertia disc 21, mounted one on top of the other by means of a torque 22. The hub 20 is mounted centered on the axis XX 'by a ball bearing 25 engaged on a central sleeve la in axial projection of the primary flywheel element 1. this bearing 25 consists of an inner ring 25a fitted on the sleeve 1a, and balls 25c, while its outer ring 25b is machined directly in the hub 20, in grade steel suitable and conventionally hardened. The interest of this provision, which allows, in addition to saving machining it provides, reduce the diametrical size of the bearing, appears clearly if we consider that passages 20c are made in the hub 20, radially above the balls 25c, opposite the bolts 8b which fix the primary flywheel 1 to the flange 8a of the engine crankshaft when the means hitch 3 are radial. These passages 20c are provided for pass an 8c bolt operating key, and, if applicable appropriate these bolts themselves. We will observe that the passages 20c are not in the plane of the figure which includes the axis of the pivot 20a of coupling means, so that there is no shown the cutting generator of passage 20c further away of axis XX '.

The torque limiter 22 is obtained by mounting at regulated friction of the disc 21 on the hub 20. At the periphery outside of the hub 20 is formed a groove 20d open on the side in the opposite direction to the primary flywheel 1 (this side external of the secondary flywheel element is the free side, for opposition with its internal side which faces the element of primary flywheel 1 and to the components comprised between the elements of steering wheel). This groove 20d has an outer cylindrical bottom 20th for centering a bore 21b made centrally in an inertia disc 21 as a whole, a disc which contributes for a major part to the mass of inertia of the element flywheel secondary 2. The groove 20d also has a sidewall 20f on the internal side, erected perpendicular to the axis XX 'of the wheel. Thus the hub 20 has at its periphery a range of cylindrical centering 20e for the disc 21.

The inertia disc 21 constitutes the reaction plate a friction clutch (the friction disc of which is illustrated in dashed lines) and for this purpose has a face 21a, here upright, to cooperate with the disc 21. This disc 21 is shaped, around the centering bore 2, in a veil with internal 21c and external 21d faces erected perpendicular to the axis XX ', and therefore parallel. The internal face 21c of the veil secondary flywheel element comes to bear against the flank 20f throat 20d. The veil is held in the throat 20d by the support under stress of a washer with axial elasticity 24 moored to hub 20, with interposition of a washer friction 23 secured in rotation to the elastic washer axial 24 by the effect of legs 23a, projecting from the inner periphery of the washer 23, and passing through 24d holes in the washer 24. The washer to axial elasticity 24 being moored on its side to the hub 20, the friction washer 23 is secured in rotation to the hub 20, while remaining free axially with respect to this hub 20, so that this friction washer 23 can lay flat on the external face 21d of the inertia disc web 21. The washer 23 is therefore transverse and reconstructs the other side of the throat.

We can easily understand the operation of the torque 22. The inertia disc web 21, clamped between the side 20f groove 20d and friction washer 23 by force axial elastic developed by the washer 24, is secured in rotation with the hub 20 as long as the torque applied to the hub 20 by the coupling means 3 will remain less than one limit torque regulated by the axial elastic force, but if the torque applied to hub 20 exceeds torque limits slippage resulting absorbs excess torque, and disc 21 does will bear that the torque limit.

The axial spring washer 24 has a part internal device 24a of transverse orientation, in which are made mooring holes, through which pass formed head rivets 20b, formed by the outer end of the pivots 20a of the coupling means 3. For by crushing the rivet heads 20b, provision has been made in the primary flywheel element 1, opposite the pivots 20a at the absence of transmitted torque, orifices 10 suitable for leaving pass a bolt (or pile) on the end of the pivots 20a. The axial spring washer 24 has, below a fold in 24c step, an external peripheral part frustoconical 24b, which is elastically deformable in the manner a Belleville washer. We see that the internal part 24a laying flat on the outer face of the hub 20, the step fold 24c extends outwards, while the peripheral part external frustoconical 24b returns inwards to support the friction washer 23 on the outer face of the disc web inertia. We understand that the fold in step 24c prohibits the transmission of axial deformations from the part external device 24b towards the internal part 24a. Through elsewhere, the orifices 24d, through which the legs 23a of the friction washer 23, are made in this step fold to allow the axial play of this washer 23.

It goes without saying that the peripheral external part 24b could be divided radially to form legs, then that here it consists of a simple washer.

Of course, the invention is not limited to examples described, but includes all variants in the context of the claims.

In particular, the bearing may be separate from the hub 20. Thus a low friction hysteresis device can intervene permanently by being located at the level of rolling. This hysteresis device, mostly worn by the central sleeve of the primary flywheel, has a washer of friction driven by the hub 20 for rubbing on the one hand, against a seat of the central sleeve of the primary flywheel, formed thanks to the change in diameter presented by said sleeve and, on the other hand, against a surface of an application washer linked in rotation, with axial mobility, to said central sleeve, and subjected to the action of an axial action elastic washer axially wedged on a washer used to wedge the ring internal bearing. The outer ring of the bearing is then axially wedged by means of a shoulder that has the internal bore of the hub 20 and of a stop, such as a retaining rings, carried internally by the hub 20. Anyway, thanks to the invention, the inertia disc 21 present at its inner periphery reduced thickness and simple shape.

Alternatively, the cassette has a tubular body external with a head for its articulation for example on the primary mass a piston secured to a rod comprising a head for its articulation on the second mass, one or more concentric springs being adapted to be compressed between the piston mounted in the tubular body and a bottom through which the rod and closing the tubular body inside which are mounted the spring (s).

Claims (9)

1. A damping double flywheel for coupling an engine to a transmission system, especially one for a motor vehicle, comprising two flywheel elements, namely a primary flywheel element (1) and a secondary flywheel element (2), which are mounted coaxially and are coupled in rotation, respectively, with the engine shaft and with an input member of the transmission system, coupling means (3) coupling the two flywheel elements together while permitting circumferential deflection to take place between them against a resilient return torque, and friction damping means (4) in parallel on the coupling means (3), the secondary flywheel element (2) including a torque limiter (22) between a hub (20) on which the coupling means (3) are articulated, and an annular inertia disc (21) that constitutes the reaction plate of a friction clutch which is the input component of the transmission system, the disc having a central bore (21b) surrounded by a radial plate portion, which is delimited by an inner face (21c) and an outer face (21d) that are at right angles to the axis of rotation (XX') of the flywheel, while the hub (20) has an annular groove (20d) which is open on the outer side, away from the primary flywheel element (1), the groove being delimited by a cylindrical base (20e) adapted for centring the central bore (21b) of the disc (21), and being delimited on the inner side by a flank (20f) adapted to bear on the inner face (21c) of the radial plate portion, the latter being maintained in the groove (20d) under controlled friction by a friction ring (23), which is coupled to the hub (20) for rotation with it and which is pressed against the outer face (21d) of the radial plate portion by an axially resilient ring (24) anchored to the hub (20), characterised in that the friction ring (23) has lugs (23a) projecting outwards and extending through apertures (24d) formed in the axially resilient ring (24).
2. A damping double flywheel according to Claim 1, characterised in that the axially resilient ring (24) is riveted on the hub (20).
3. A damping double flywheel according to Claim 2, characterised in that the rivets (20b) of the axially resilient ring (24) constitute pivots (20a) for bearings of the coupling means (3).
4. A damping double flywheel according to Claim 2 or Claim 3, characterised in that the primary flywheel element (1) has, in facing relationship with the location of the rivets (20b) of the axially resilient ring (24) when the resilient return torque is zero, apertures (10) for passage of a riveting tool therethrough.
5. A damping double flywheel according to any one of Claims 1 to 4, characterised in that the radially resilient ring (24) includes an inner peripheral portion (24a) with holes for anchoring the ring on the hub (20), and, beyond a cranked portion (24c), an elastically deformable, frusto-conical, outer portion (24b).
6. A damping double flywheel according to Claim 5, characterised in that the outwardly projecting lugs (23a) of the friction ring (23) project from the inner periphery of the said ring, and the apertures (24d) for passage of the said lugs in the axially resilient ring (24) are formed in the cranked portion (24c).
7. A damping double flywheel according to any one of Claims 1 to 6, characterised in that, the secondary flywheel element (2) being mounted coaxially with the first flywheel element (1) by means of a ball bearing (25) having balls (25c), which is mounted through an inner ring (25a) on a sleeve (1a) that projects from the primary flywheel element (1), the hub (20), which is of hardened metal, constitutes the outer ring (25b) of the ball bearing (25).
8. A damping double flywheel according to any one of Claims 1 to 7, characterised in that the hub (20) has passages (20c) to admit at least one key for the purpose of manoeuvring bolts (8b) which fasten the primary flywheel element (1) on a terminal flange (8a) of the crankshaft of the engine.
9. A damping double flywheel according to any one of Claims 1 to 8, characterised in that the radial plate portion of the inertia disc (21) is of reduced thickness.

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